Re: Mother's milk
You are right PCG... but the ayah suggests that mother should not breast feed for more than two years anyway. The sugession however emphasize for TWO WHOLE YEARS.. so there goes the reference you asked for...
Also in surah At Talaq, there is a mention of finding another woman for breast feeding if mother can not but that context is when there is a divorce between the two at or near the time of birth of the child... (you know foster mother) ...
but as you also mentioned if mother can't, there is no forcing involved... I just gave you the reference you were looking for :-)